﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Web;

namespace CoreSolution.Tools
{
    internal class ParameterReplacer : ExpressionVisitor
    {
        public ParameterReplacer(ParameterExpression paramExpr)
        {
            this.ParameterExpression = paramExpr;
        }

        public ParameterExpression ParameterExpression { get; private set; }

        public Expression Replace(Expression expr)
        {
            return this.Visit(expr);
        }

        protected override Expression VisitParameter(ParameterExpression p)
        {
            return this.ParameterExpression;
        }
    }

    #region 这段代码将会和 Core ExpressionBuilder 之间会有影响，两者是不同概念（故先将其注释掉）
    //public static class PredicateExtensions
    //{
    //    public static Expression<Func<T, bool>> True<T>() { return f => true; }

    //    public static Expression<Func<T, bool>> False<T>() { return f => false; }

    //    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> exp_left, Expression<Func<T, bool>> exp_right)
    //    {
    //        var candidateExpr = Expression.Parameter(typeof(T), "candidate");
    //        var parameterReplacer = new ParameterReplacer(candidateExpr);

    //        var left = parameterReplacer.Replace(exp_left.Body);
    //        var right = parameterReplacer.Replace(exp_right.Body);
    //        var body = Expression.And(left, right);

    //        return Expression.Lambda<Func<T, bool>>(body, candidateExpr);
    //    }

    //    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> exp_left, Expression<Func<T, bool>> exp_right)
    //    {
    //        var candidateExpr = Expression.Parameter(typeof(T), "candidate");
    //        var parameterReplacer = new ParameterReplacer(candidateExpr);

    //        var left = parameterReplacer.Replace(exp_left.Body);
    //        var right = parameterReplacer.Replace(exp_right.Body);
    //        var body = Expression.Or(left, right);

    //        return Expression.Lambda<Func<T, bool>>(body, candidateExpr);
    //    }
    //}
    #endregion
}